prove that (cos5x+cos4x)/2cos3x-1 =cosx+cos2x
Shreya Chandwadkar , 13 Years ago
Grade 11
Trigonometry> prove the following...
1 AnswersRinkoo Gupta
Last Activity: 10 Years ago
To prove (cos5x+cos4x)/2cos3x-1 =cosx+cos2x
I.e. To prove cos5x+cos4x=(2cos3x-1)(cosx+cos2x)
RHS=(2cos3x-1)(cosx+cos2x)
=2cos3xcosx+2cos3xcos2x-cosx-cos2x
=cos4x+cos2x+cos5x+cosx-cosx-cos2x
=cos4x+cos5x=LHS
Thanks & Regards
Rinkoo Gupta
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